Passenger cars have nowadays a number of safety restraint systems, such as seat belt pre-tensioners or airbags, as e.g. front and side airbags, which serve to cushion or limit the impact of a passenger with for example interior parts of passenger cars in case of an accident. Deceleration sensors in the passenger vehicle detect high deceleration values as they occur in case of an accident and send a trigger signal via a wire or cable to SRS devices. An explosive device, known as a squib, inflates the airbag or tightens the belt. The wires or cables from the deceleration sensor are connected to an electronic control unit and then to the squib by means of a so called squib connector. To this aim, the squib is usually provided with a socket or receptacle which contains two contact pins. The squib connector comprises a plug part or plug-connector corresponding to the socket, which plug part has two receptacles for the reception of the contact pins of the squib socket. To improve the connection between squib and plug connector, retainer inserts were developed, which are adapted to fit into the receptacle of standardized squibs and which facilitate and secure the connection between squib and plug connector. These retainer inserts are commonly provided with some kind of a shorting clip, which short circuits the contact pins of the squib before a plug-connector is connected to the squib and which retainer insert further provides mechanical fastening means for a secure mechanical connection of plug-connector with the squib receptacle. The retainer inserts are sometimes also referred to as shorting inserts.
The principle structure of an (airbag) squib is for example described in WO 2004/020933. The squib disclosed in this document comprises an outer can enclosing a suitable pyrotechnic charge and an igniter which is provided with two contact pins being electrically connected to an igniter wire which can activate the charge of the squib. The igniter further includes a retainer for securing the squib to the housing of e.g. an airbag inflator, which retainer further comprises a plastic insert, which is injection moulded around the pins of the squib and which serves to provide for a mechanical fastening with the corresponding (squib) plug connector. The retainer is further provided with a so called shorting clip, which is usually an electroconductive metallic spring part, which in the non-coupled condition electrically connects the two pins of the squib with each other, i.e. shorting the same. The shorting of the contact pins serves to prevent an unintended explosion of the pyrotechnic charge due to electrical potential differences occurring between the two contact pins, for example during transport or handling. The short circuit established by the shorting clip is lifted and opens upon correct coupling of the corresponding plug-connector into or with the retainer. Usually, a contacting member of a shorting clip is displaced by the plug part of the plug-connector so that the two contact pins are no longer electrically connected.
The shorting clips of the prior art in use today are not only intended to prevent an unintentional ignition of the charge of the squib but they also serve as a control or monitoring means of the correct coupling of the squib plug-connector with its counterpart, i.e. the squib receptacle respectively the retainer or insert mounted therein. Upon correct coupling of the plug-connector with its counterpart, the short circuit between the contact pins of the squib is automatically open as described above, and this can be detected by means of suitable electrical/electronic monitoring means, as it is well known to the skilled person.
On the one hand, the necessary provision of the above described shorting clips leads to a significant increase in production costs, since not only a separate part has to be provided and assembled but also since the provision of a shorting clip in a retainer or airbag receptacle limits the design freedom for squib connectors thereby further increasing the costs since it is very often not possible to use the optimum design for plug-connector and retainer due to the necessary regard for the shorting clip.
On the other hand, constant improvements were made for the squib making it more secure. In the latest developments, modern squibs are so reliable that a shorting clip is no longer absolutely necessary. Thanks to the improvements, an unintended ignition of the charge due to an electrical potential difference between the contact pins can be ruled out. Thus, for this new type of squibs, the shorting clips could be disposed off, thereby reducing the manufacturing costs for the squib connectors considerably. However, as was mentioned above, the shorting clip is not only a safety feature for an unintended ignition of explosive charge of the airbag or belt pre-tensioner system but it is also commonly used to monitor the correct coupling of the plug-connector with its counterpart. Without a shorting clip, this is no longer possible with the existing connector systems so that shorting clips are still necessary for their monitoring function, although the “shorting function” itself is no longer strictly necessary.
It is therefore an object of the present invention to provide a connector for a safety restraint system which allows the electrical or electronic monitoring of the correct coupling of a (squib) plug-connector with its corresponding counterpart, like for example a squib receptacle or a retainer insert for a squib receptacle. It is a further object of the invention to provide a connector with such a monitoring function, which is cheaper to produce than the known connectors comprising shorting clips and which is of a more flexible construction.
These and other objects, which become apparent upon reading the following description, are solved by connectors according to claims 1 and 8.